Girder End Cracking In Prestressed I Girders

T. Patrick Earney

Department of Civil and Environmental Engineering, University of Missouri – Columbia, USA

There has been much interest in the stresses created during the early-age of a prestressed concrete girder. A recently completed research project to instrument and monitor Missouri’s first HPC Bridge (Gopalaratnam and Eatherton, 2001) provided some useful insights regarding the early-age response of HPC prestressed girders.

This project was undertaken on behalf of the Missouri Department of Transportation (MoDOT) after cracking was observed in more than 100 of the 900 PC I-girder bridges in the state. The data from a previous project that instrumented four HPC girders in Missouri’s first HPC bridge provided the information needed to analyze the early-age behavior of these girders (Eatherton, 1999). The instrumentation in these girders was monitored from the beginning of the girder’s casting until one year after the opening of the bridge. The instrumentation consisted of thermistors, strain gaged bars, and vibrating wire strain gages at several locations in each of two cross sections. Additionally, two stirrups were instrumented with strain gages at the end of each girder.

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